#include "Mystdio.h"

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <assert.h>
#include <unistd.h>

#define FILE_MODE 0666

_FILE * _fopen(const char* filename, const char* flag)
{
  assert(filename);
  assert(flag);
  
  int f = 0;
  int fd = -1;
  if(strcmp(flag,"w")==0)
  {
    f = (O_CREAT|O_WRONLY|O_TRUNC);
    fd = open(filename,f,FILE_MODE);
  }
  else if(strcmp(flag,"a")==0)
  {
    f = (O_CREAT|O_WRONLY|O_APPEND);
    fd = open(filename,f,FILE_MODE);
  }
  else if(strcmp(flag,"r")==0)
  {
    f = O_RDONLY;
    fd = open(filename , f);
  }
  else 
  {
    return NULL;
  }

  if(fd == -1) return NULL;

  _FILE* fp = (_FILE*)malloc(sizeof(_FILE));
  if(fp == NULL) return NULL;

  fp->fileno = fd;
  fp->flag = FLUSH_LINE;
  //fp->flag = FLUSH_ALL;
  fp->out_pos=0;

  return fp;

}

//FILE中的缓冲区的意义是什么？
//若是不急于刷新的缓冲区每次都刷新相较于将所有输出内容拷贝到数组中后一起刷新的效率低
//因此缓冲区的存在的意义之一就是提高效率
int _fwrite(_FILE* fp, const char* s, int len)
{
  memcpy(&fp->outbuffer[fp->out_pos],s,len);
  fp->out_pos += len;

  if(fp->flag&FLUSH_NOW)
  {
    write(fp->fileno,fp->outbuffer,fp->out_pos);
    fp->out_pos = 0;
  }
  else if(fp->flag&FLUSH_LINE)
  {
    if(fp->outbuffer[fp->out_pos-1]=='\n')
    {
      //不考虑其他情况
      write(fp->fileno,fp->outbuffer,fp->out_pos);
      fp->out_pos = 0;
    }
  }
  else if(fp->flag&FLUSH_ALL)
  {
    if(fp->out_pos == SIZE)
    {
      write(fp->fileno,fp->outbuffer,fp->out_pos);
      fp->out_pos = 0;
    }
  }
  //未作异常处理和局部问题  
  return len;
}

void _fflush(_FILE* fp)
{
  if(fp->out_pos > 0)
  {
    write(fp->fileno,fp->outbuffer,fp->out_pos);
    fp->out_pos = 0;
  }
}

void _fclose(_FILE* fp)
{
  if(fp==NULL) return;
  _fflush(fp);
  close(fp->fileno);
  free(fp);
}
